>>The GetLogicalDriveStrings function will only return a list of drives available. You will next need to use GetDriveType function, again in Win32API to identify the type of drive. If it returns DRIVE_CDROM, you then have the drive letter of the CDROM. It may be quicker just to scan drives A to Z with this function - need to manually test to see if error occurs on non existent drive. Then stop when you find CD.
>
>Not necessarily stop - I've managed once to add a disk and have the CD as the non-last drive. Don't remember how I did it, but I think the letter was reserved for a inaccessible network mapping, and then the CD just took that letter. I know it was something unexpected - and yet having the CD as the last drive is just a default, not a mandatory thing. So he better check all available drives if it's not only the CD he's looking for.

It's easy under NT, where Disk Administrator lets you shift drive letter assignments all over creation, and if you have removable media drives like the Zip or Syquest stuff that set the drive letter up in the AUTOEXEC.BAT under Win9x, the removable drive letter is added after the CD in many cases, which is a native protected-mode device.